Archived Grid heater not shutting down

[JoeFreeman]

Shut down the truck and about 1-2 hours later batteries completely drained. Dealer replaced grid heater took it home and the same thing happened. Finally it occured at the dealer so the mechanic could feel the air horn overheating because the heater kept cycling even after the key was off. We used a light tester and sure enough it was cycling power to the heater. They tapped the solenoid and it occurred again. I have a hunch if they replace the solenoid and the rlay it will solve the problem. What do you think? Your opinions are very welcome.



John





99 Quad 4x4 24valve Auto Black

 

[fest3er]

Yes. At least one of your heater relays has failed (the spring has become too soft to keep the contactor away from the contacts inside the relay!)



Yes, if the dealer replaces the relay set, the problem will vanish. But it will return. The relays DC use are ... marginal for the application.



If you want a better solution, grab http://home.adelphia.net/~npmrphy/relay.pdf and print it. It's a one-page description of how I installed a set of better relays in my truck.



Fest3er

 

[Skydiver]

Mine stick also.

Hey Fest3er,

Please check the web site. I can't get it to open.

I am very interested in new and better relays.

Tim

 

[fest3er]

Re: Mine stick also.

Originally posted by Skydiver

Please check the web site. I can't get it to open.

Oops! Too many *similar* logins. The link works now. (I *knew* I shoulda checked it!!)



Fest3er

 

[illflem]

Though the relays are probably the problem another cause I've seen is failure of the intake air temp sender. It can send a signal to the PCM saying the temp is too low and needs heat. If the problem is the sensor the PCM still won't let the heaters come on unless you are going slower than 16 mph.

 

[Michael Hughes]

If it was the AIT sensor, I would think the grid heaters would cylce. Plus, he is having problems with the engine shutdown.

 

[fest3er]

Originally posted by illflem
Though the relays are probably the problem another cause I've seen is failure of the intake air temp sender. It can send a signal to the PCM saying the temp is too low and needs heat. If the problem is the sensor the PCM still won't let the heaters come on unless you are going slower than 16 mph.

This would be true if the heaters were cycling normally yet needlessly when the engine is running or the key has been turned on. But when the heaters turn on when the key is off, it can *only* be a failed heater relay (or both failed).

Fest3er